A former elementary principal has filed a sex discrimination lawsuit against a Southern California school district, claiming she was demoted and reassigned because she was pregnant and unmarried.

Christine Castillo alleges she was discriminated against by La Cañada Unified School District Superintendent Wendy Sinnette, among other employees with the district in La Cañada Flintridge, California, when she told them she was expecting a child in 2012, NBC4 reported.

In a suit filed Dec 28 through the Los Angeles County Superior Court, Castillo claims the district denied her a doctor's recommendation for reduced hours during pregnancy and later conducted negative employee evaluations.

Christine Castillo has filed a sex discrimination suit against La Cañada Unified School District

This led to her being reassigned to a teaching position for the 2015-16 school year.

Sinnette allegedly made statements to Castillo, such as 'This is really going to upset your staff and parents', 'I made it clear what this job required' and 'I need a drink'.

The lawsuit also states that Sinnette told Castillo she should have told the district about her pregnancy sooner.

'This is something you would have expected to hear in the 19th or 18th century.

'For the school district to state that being pregnant is a scarlet letter on a woman - that's a problem if the community really feels that way', said Ben Meiselas, Castillo's attorney.

The former La Cañada Elementary School principal claimed the Southern California district demoted and reassigned her to a classroom position because she was pregnant and unmarried

Castillo - who gave birth to daughter Alissa on Dec. 19, 2012 - was hired by the district in July of that year and told them she was pregnant the following month.

'When the words came out of my mouth, I could just see her body just freeze. Her face just looked so disappointed', Castillo said of Sinnette's reaction to the news.

Previously, Castillo filed an internal complaint against the school district in April 2015, which led to an investigation.

Documents from the internal investigation obtained by NBC4 show that Sinnette and the former superintendent of human resources Patricia Hager were concerned that Castillo's pregnancy would spark a negative reaction in the community because she was unmarried at the time.

Castillo moved from Seattle to Los Angeles in 2012 after she was hired as principal

When the district notified Castillo in mid-June 2015, with results of the internal investigation still pending, that she would be reassigned to a teaching position she resigned.

That same evening the district announced that Emily Blaney, a technology integration teacher on special assignment, had been selected as the school's principal for the following school year.

'It is unfortunate that representatives for Ms Castillo are pursuing a legal strategy that has nothing to do with the facts.

'Her placement into the classroom last year had absolutely nothing to do with her maternity leave of four years ago', said school board member Ellen Multari in a statement.